2022 Introduction to Statistics in Research Mitchell 2nd ed

I N T R O T O R E S E A R C H : D A T A V I S U A L I Z A T I O N & C O M M O N S T A T T E S T S

Q2 Was the sample selected in a reasonable way?

Answer: Yes, the researchers randomly selected fast-food restaurants.

Q3 Is the sample likely to be

Answer: Yes, the researchers randomly selected the fast-food restaurants, and it is reasonable to expect the people eating at these locations as representative. Answer: Yes, two potential sources of bias. 1) Response bias since customers were approached before they ordered; and 2) Non-response - some people refused to participate.

representative of the population of interest?

Q4 Are there any obvious sources of bias?

Experimental Design Studies There are key concepts of an experimental design. Let's start by defining some terms.

Direct control holds potential confounding variables constant so their effects are not confounded with the treatments.

Blocking uses potentially confounding variables to create groups (blocks) that are similar. All experimental conditions (treatments are then tried in each block.

Random assignment removes the potential for confounding variables by creating equivalent experimental groups.

Replication ensures that there is an adequate number of observations for each treatment.

It is a common practice to use volunteers as subjects in an experiment. Random assignment of the volunteers to treatments allows for cause-and-effect conclusions. But this does limit the ability to generalize to the population.

To really understand confounding variables, let's watch this short two-minute video.

Doty, D. (2013, Aug 27). Research Methods: Extraneous and Confounding Variables. ByPass Publishing. [Video]. YouTube. Retrieved from https://youtu.be/Qe7wN8qT8ic

More Experimental Design

Experimental research deals with cause-and-effect relationships. A good website for learning about experimental design is Stat Trek - Teach yourself statistics.

58